WO2000014029A1

WO2000014029A1 - Monolithic ceramic material comprising an antimicrobial material

Info

Publication number: WO2000014029A1
Application number: PCT/GB1999/002925
Authority: WO
Inventors: Ian Birkby; John Vivian Wood
Original assignee: DYNAMIC CERAMIC Ltd
Current assignee: DYNAMIC CERAMIC Ltd
Priority date: 1998-09-05
Filing date: 1999-09-03
Publication date: 2000-03-16
Anticipated expiration: 2001-03-05
Also published as: AU5640399A; GB9819303D0

Abstract

A solid monolithic ceramic material comprising an antimicrobial material, such as silver chloride, on a surface part thereof. The antimicrobial material may be keyed to surface formations and/or provided in pores, and may be applied to the ceramic as a glaze or sol-gel.

Description

MONOLITHIC CERAMIC MATERIAL COMPRISING AN ANTIMICROBIAL MATERIAL

This invention concerns a solid monolithic material with antimicrobial properties and a method for making same, and especially such a material usable in cutting applications such as in knives, surgical equipment, razors, food processing and handling equipment, undersea applications such as pumps and the like, etc.

In many applications such as cutting during surgery, food preparation or for instance shaving, infection can often set in. This can be due to unclean conditions and/or an unclean cutting blade. In undersea applications such as in pumps and the like, problems can be encountered with biofouling.

According to the present invention there is provided a solid monolithic material, the solid material comprising a ceramic material with an antimicrobial material provided on the surface thereof or incorporated into at least a surface part thereof.

The antimicrobial material may be keyed on to formations on the surface of the ceramic material. The formations may comprise micro indentations or other similar features, which features preferably have a dimension of less than 25 μm and desirably less than 5 μm. Alternatively or in addition the formations may comprise macro surface effects, which may have a diameter of up to 1 mm or in some instances even bigger. The surface effects may comprise any of scratches, holes, dimples or shaped indentations.

Alternatively or in addition, the antimicrobial material may be provided within pores in the ceramic material, and desirably in pores substantially only in a surface part of the ceramic material. The ceramic material may be provided with a surface part of greater porosity than the remainder. The pores may comprise macro formations, or alternatively the pore size is preferably less than 25 μm and desirably less than 5 μm. The pores may be formed in the surface of the ceramic material, and desirably with a narrow opening relative to the remainder of the pore.

The ceramic material is preferably zirconia.

The antimicrobial material preferably comprises a compound which releases metal ions, which may be gold, silver or copper, over time in aqueous conditions. The antimicrobial material preferably releases silver ions over time and may comprise a low soluble silver salt such as silver chloride.

The metal releasing compound is preferably held on a support material. The support material is preferably physiologically inert, being insoluble and stable in aqueous conditions. The support material preferably comprises an inert oxidic synthetic particulate material, which preferably has a high surface area relative to its nominal geometric surface area. The support material may be titanium dioxide, and may comprise one or more of the crystallised forms of titania, namely anatase, rutile and brookite.

Alternatively, the support material may comprise a ceramic material.

The antimicrobial material may be applied as part of a glaze, which is fired after application.

The invention also provides a method of making a solid material according to any of the preceding eight paragraphs.

The antimicrobial material may be applied onto or into the ceramic material by spraying, dipping or other liquid application.

The antimicrobial material may be applied as part of a glaze or a suspension.

When applied as a glaze, the solid material is preferably fired following application of the glaze thereto. The glaze may be applied to the whole of a surface of surfaces ofthe solid material, and then the glaze removed from said surface or surfaces apart from the formations thereon.

Alternatively the antimicrobial material may be provided with a binder material, which binder material may be applied as a sol-gel and subsequently dried. Alternatively the binder material is a polymer which may be thermosetting or thermoplastics.

The formations on the surface of the ceramic material may be formed by a press tool surface finish, etching, micro laser machining, micro lithography, drilling, machining or abrading. The formations may be formed prior to firing of. the ceramic material.

The porosity of the ceramic material may be achieved by sintering a compact at a temperature lower than that required to generate a fully dense material.

Alternatively, the ceramic material could be formed by sintering a body member under optimum conditions, and subsequently forming a surface member on the body member and compacting and/or heating at a lower pressure or temperature to provide a required porosity in the surface member.

As a further alternative, a required porosity could be formed in the ceramic material following formation thereof. The porosity could be formed by laser micro machining or micro lithography. The pores could be formed with a narrow opening relative to the dimension of the main body thereof.

The invention further comprises a ceramic article made by a method according to any of the preceding eight paragraphs.

The article may be in the form of a blade, and when made with a ceramic material having a surface area of increased porosity, the tip of the blade may be formed of the body member by removing the surface member from that part, by for instance machining.

Examples of how the invention can be carried out will now be described by way of illustration only.

Ceramic materials can be used in a wide range of applications and zirconia has for example been found to be particularly suitable for cutting applications, providing an increased longevity of for instance thirty to fifty times that of a conventional metal blade. Such applications may be in surgery, food processing or handling, or manufacture. Ceramic materials can also be used in parts for pumps and the like usable under sea. In such conditions there is a potential problem with biofouling.

In the present invention an antimicrobial material is incorporated into the surface of a ceramic material. The antimicrobial material may be applied on to the surface of the material by spraying, dipping or other liquid application. The surface of the ceramic material would be keyed prior to application by for example providing micro indentations or other formations, typically with a dimension of 3-5 μm. These formations could be provided by laser machining or using micro lithography in a similar technique to that used in silicon wafer production.

Alternatively, the surface may be keyed with macro surface effects such as scratches, holes, dimples or shaped indentations. These may be achieved by drilling, machining or abrading, and may be produced in the ceramic material prior to firing. The surface features may have a dimension of up to 1mm or even larger.

An antimicrobial material as described in European Patent No. 0251783 (J-Mac (trademark)) would be suitable. This material comprises silver chloride held on titania in the form of one or more of anatase, rutile or brookite. This material could be applied as a suspension or a sol-gel. Two preparation routes for this material are provided below. Alcohol suspension route - A 1% J-Mac suspension in alcohol was prepared in a dark room. These red light conditions ensured no premature degradation of the J-Mac by white light. High purity methanol with less than 0.0025% H O was used in order to prevent reaction between J-Mac particles and water.

The suspension was stirred continuously over a 24 hour period after which time the samples were removed and thoroughly rinsed in high purity methanol (all performed under dark room conditions). The infiltrated ceramic samples were then wrapped in aluminium foil (to prevent light contamination) and transferred to an drying oven. Samples were dried at 110°C for 5 hours.

Sol-Gel processing route - The sol-gel route detailed in this section leads to an alumina based coating on the surface of the ceramic material. Processing was performed again under dark room conditions. A 2% suspension of J-Mac in water was first of all prepared (1ml of J-Mac in 50ml of H₂0). The ceramic material samples were then introduced into the suspension and stirred continuously. Aluminium nitrate was added to give a total liquid volume of 100ml (i.e. 1% J-Mac concentration). Using a pH meter to monitor acidity, the suspension was brought to neutral pH 7 by carefully adding ammonium hydroxide via a dropper. The samples were then removed from the sol-gel, wrapped in aluminium foil and dried for 24hrs at 350°C to form a ceramic. The overall chemical process may be described by:

^A1<^N0Λ₍._q, ^{+ m}4^0HW → ^A1<^0H»3<S, ^{+ 3NH} _M ^{+ 3N}°3 ,a_q, ₂A1(0H)_3(S) — 350°C→Al₂O_3(a - 3H.0

The sol-gel route retains and binds the J-Mac particles providing for a controlled release of the antimicrobial ions. The sol-gel route material can be incorporated into larger holes in the ceramic surface such as for example could be provided by drilling upto a diameter of around 1mm. As the ceramic wears down, further J-Mac particles held in the hole by the binder will reach the surface and therefore release the antimicrobial ions. Other sol-gel routes may be suitable based on for example titanium or silicon.

An alternative approach is to use an antibacterial agent such as AM 15 (trade mark "SUMITOMO OSAKA CEMENT COMPANY LIMITED"). This is a ceramic powder containing a silver salt which has the following composition:

SiO₂ 56%

Ag₂0 24%

Al₂O3 10%

P2O 5%

Ig.loss 3%

Other 2%

The material was added at 8.75% by weight to a typical sanitaryware glaze (which contained a small amount of colouring oxide) with the following composition:

Raw Materials Weight %-

Feldspar 27

Quartz Sand 28

China Clay 10

Calcium Carbonate 13

Barium Carbonate 5

Zinc Oxide 4

Zircon 13

The glaze was then milled continuously for a period of 48 hours. This ensured that 85% of the particles were below 5μm in diameter, this was important to ensure that sufficient particles could enter the surface imperfections. The glaze was then applied to ceramic substrates with appropriate surface formations, by brushing, dry spraying, dipping and wet spraying. Excess glaze was removed with a soft cloth or a palette knife. The ceramic substrates were then fired with a ramp of 100°C per hour to a peak temperature of 1200°C and a dwell of one hour, and natural cooling was allowed to take place.

Another way of providing the antimicrobial material is within pores of the ceramic. Such pores could be provided by sintering a ceramic at a lower temperature than that required to generate a fully dense material. Zirconia ceramics would be particularly suitable in the present invention. With a zirconia such as HSY3-SD Yttria - Tetragonal Zirconia Poly crystalline Material this would mean sintering at a temperature below 1450°C.

With a view to providing the usual structural integrity of such a zirconia, a core could be provided with a fully dense structure, having been sintered under optimum conditions. A surface layer could then be formed around this core and compacted at a lower pressure to provide a porous outer skin.

When a blade is formed from such a material, at the tip of the blade the outer skin could be removed to provide the hardest possible blade but with the antimicrobial material containing material around it, releasing silver ions to counter infection.

It may be possible for the antimicrobial material to be introduced into the pores by liquid techniques as outlined above. Alternatively, it may be necessary for pressure to be applied to urge the material into the pores.

There are thus described materials which provide the advantages of ceramic material, which are being increasingly appreciated in a wide range of situations, with the use of an antimicrobial material to avoid infection or biofouling or other problematic developments. This material is ideally suited for a wide range of applications such as knives and other cutting devices for use in food preparation and processing, for use in surgery and other medical cases, for use in shaving, for use in food preparation and handling equipment in general, or for use in marine situations to prevent biofouling.

A wide range of modifications may be made in addition to those outlined above. For example, a wide range of ceramic materials could be used. A different antimicrobial material may be usable, which may for instance release gold, copper, or other metal ions rather than silver. Different techniques for combining the two materials could be used. Different size pores or other formations may be provided.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1. A solid monolithic material characterised in that the solid material comprises a ceramic material with an antimicrobial material provided on the surface thereof or incorporated into at least a surface part thereof.

2. A material according to claim 1, characterised in that the antimicrobial material is keyed on to formations on the surface of the ceramic material.

3. A material according to claim 2, characterised in that the formations comprise micro indentations or other similar features.

4. A material according to claim 3, characterised in that the micro indentations or other similar features having a dimensions of less than 25 μm.

5. A material according to claim 4, characterised in that the micro indentations or other similar features have a dimension of less than 5 μm.

6. A material according to any of claims 2 to 5, characterised in that the formations comprise macro surface effects.

7. A material according to claim 6, characterised in that the macro surface effects have a diameter of up to 1mm.

8. A material according to claims 6 or 7, characterised in that the surface effects comprise any of scratches, holes, dimples or shaped indentations.

9. A material according to any of the preceding claims, characterised in that the antimicrobial material is provided within pores in the ceramic material.

10. A material according to claim 9, characterised in that the antimicrobial material is provided in pores substantially only in a surface part of the ceramic material.

11. A material according to claims 9 or 10, characterised in that the ceramic material is provided with a surface part of greater porosity than the remainder.

12. A material according to any of claims 9 to 11, characterised in the pores comprise macro formations.

13. A material according to any of claims 9 to 11, characterised in that the pore size is less than 25 μm.

14. A material according to claim 13, characterised in that the pore size is less than 5 μm.

15. A material according to any of claims 9 to 14, characterised in that the pores are formed in the surface of the ceramic material.

16. A material according to any of claims 9 to 15, characterised in that the pores are formed with a narrow opening relative to the remainder of the pore.

17. A material according to any of the preceding claims, characterised in that the ceramic material is zirconia.

18. A material according to any of the preceding claims, characterised in that the antimicrobial material comprises a compound which releases metal ions, over time in aqueous conditions.

19. A material according to claim 18, characterised in that the antimicrobial material comprises gold, silver or copper.

20. A material according to claim 19, characterised in that the antimicrobial material comprises a low soluble silver salt.

21. A material according to claim 20, characterised in that the antimicrobial material comprises silver chloride.

22. A material according to any of claims 18 to 21, characterised in that the metal releasing compound is held on a support material.

23. A material according to claim 22, characterised in that the support material is physiologically inert, being insoluble and stable in aqueous conditions.

24. A material according to claim 23, characterised in that the support material comprises a particulate material which has a high surface area relative to its nominal geometric surface area.

25. A material according to claims 23 or 24, characterised in the support material comprises an inert oxidic synthetic particulate material.

26. A material according to any of claims 23 to 25, characterised in that the support material is titanium dioxide.

27. A material according to claim 26, characterised in the support material comprises one or more of the crystallised forms of titania, namely anatase, rutile and brookite.

28. A material according to claims 23 or 24, characterised in that the support material comprises a ceramic material.

29. A material according to any of the preceding claims, characterised in that the antimicrobial material is applied as part of a glaze, which is fired after application.

30. A method of making a solid material characterised in that the material is according to any of the preceding claims.

31. A method according to claim 30, characterised in that the antimicrobial material is applied onto or into the ceramic material by spraying, dipping or other liquid application.

32. A method according to claims 30 or 31, characterised in that the antimicrobial material is applied as part of a suspension.

33. A method according to claims 30 or 31, characterised in that the antimicrobial material is applied as part of a glaze.

34. A material according to claim 32, characterised in the solid material is fired following application of the glaze thereto.

35. A material according to claims 33 or 34, characterised in that the glaze is applied to the whole of a surface of surfaces of the solid material, and then the glaze removed from said surface or surfaces apart from the formations thereon.

36. A material according to any of claims 30 to 32, characterised in that the antimicrobial material is provided with a binder material.

37. A material according to claim 36, characterised in that the binder material is applied as a sol-gel and subsequently dried.

38. A material according to claim 36, characterised in that the binder material is a polymer which may be thermosetting or thermoplastics.

39. A material according to any of claims 30 to 38 when dependent on claim 2 or on any of claims 3 to 29 when dependent on claim 2, characterised in that the formations on the surface of the ceramic material are formed by a press tool surface finish, etching, micro laser machining, micro lithography, drilling, machining or abrading.

40. A material according to any of claims 30 to 39 when dependent on claim 2 or on any of claims 3 to 29 when dependent on claim 2, characterised in that the formations are formed prior to firing of the ceramic material.

41. A material accotding to any of claims 30 to 40 when dependent on claim

9 or on any of claims 10 to 29 when dependent on claim 9, characterised in that the porosity of the ceramic material is achieved by sintering a compact at a temperature lower than that required to generate a fully dense material.

42. A material according to any of claims 30 to 40 when dependent on claim

10 or on any of claims 11 to 29 when dependent on claim 10, characterised in that the ceramic material is formed by sintering a body member under optimum conditions, and subsequently forming a surface member on the body member and compacting and/or heating at a lower pressure or temperature to provide a required porosity in the surface member.

43. A material according to any of claims 30 to 40 when dependent on claim 10 or on any of claims 11 to 29 when dependent on claim 10, characterised in that a required porosity is formed in the ceramic material following formation thereof.

44. A material according to claim 43, characterised in that the porosity is formed by laser micro machining or micro lithography.

45. A material according to claims 43 or 44, characterised in that the pores are formed with a narrow opening relative to the dimension of the main body thereof.

46. A ceramic article, when dependent on claim 10 or on any of claims 11 to 45 when dependent on claim 10, characterised in that the article is made by a method according to any of the preceding claims.

47. An article according to claim 46, characterised in that the article is in the form of a blade.

48. An article according to claim 47, when dependent on claim 10 or on any of claims 11 to 45 when dependent on claim 10, characterised in that the tip of the blade is formed of the body member by removing the surface member from the surface area of increased porosity by for instance machining.